Historically, existing internal combustion engine vehicles have not been converted to hybrid vehicles because of the complexity and lack of space to incorporate the electric motors into the drivetrain. It is desired to be able to convert existing conventional vehicle designs to create hybrid electric vehicles. For example, it is desirable to improve the efficiency and performance of a rear-wheel drive vehicle by retrofitting the mechanical design to include independently controllable electric motors, an energy storage system, motor control units and a supplemental vehicle sensing and control unit. One such conventional design that may benefit from such a retrofit is a front engine, rear drive vehicle, more specifically a front internal combustion engine arrangement, having a transmission and a rear differential driving the rear wheels. The most direct route to providing electric power to these vehicles is to remove the internal combustion engine and sometimes the transmission. An electric motor is placed in the resulting empty front internal combustion engine bay and the electric motor is coupled in line to the existing rear differential. This approach adds significant weight to the vehicle due to the large battery packs and in some cases the large conventional electric motors that are necessary to duplicate the power and driving range of the internal-combustion-engine-driven vehicle. Further, the removal of the internal combustion engine results in the necessity to recharge the batteries from the electrical grid and limits the driving range and utility of the vehicle.
It is desirable to be able to utilize existing conventional internal combustion engine vehicle designs, for example front engine, rear drive designs, but to retrofit those designs in a robust way that results in efficient use of space while greatly improving the performance and efficiency of the vehicle. Further, it is desirable to retrofit existing vehicles with supplemental electric systems to produce efficient, high performance vehicles with extended driving range. Accordingly, there is a need for a vehicle hybrid drive arrangement for motor vehicles that allows existing conventional vehicle designs to be efficiently converted to hybrid electric vehicles. Furthermore, there is a need for a hybrid drive arrangement that allows for compact new vehicle designs that readily incorporate electric motors in a rear transaxle arrangement, while incorporating an independent suspension benefiting performance and efficiency.